Monday, January 22, 2007

Lacrosse 5 tricks again, and Lacrosse 4 cruising near the Pleiades

Another clear (and cold) evening. I observed the radar birds Lacrosse 5 (05-016A) and Lacrosse 4 (00-047A) within a minute of each other (making the imaging quite hectic, having to swap the camera to a different part of the sky within a few tens of seconds).

I obtained two images (hence 4 positions) on Lacrosse 4, the first one of which captured the sat cruising at a steady mag. +3 close to the Pleiades cluster (image below):

(click image to enlarge)

A minute earlier I had captured Lacrosse 5 in the act of doing its infamous "disappearance trick" again. The image below shows it fading rapidly, in fact the apparent trail end on the image predates the end of the exposure. Visually, I timed the disappearance at about 18:25:30 (+/- 2s) UTC.

(click image to enlarge)

I dropped the second point on Lacrosse 5 as it probably does not represent the position at the end of the exposure, but rather the point where it became too faint for the camera. The first points suggest it was perhaps some 0.15s late and on-track.

Lacrosse 4 was perhaps some 0.2s late (delta T's vary a bit between 0.05s and 0.30s) and somewhat off-track (about 0.05 degree).


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